Thermoplastic resins having high heat-resistance and chemical-resistance, such as aromatic polyamide resins, can be used in the production of various products such as electrical/electronic parts, automobile parts, optical parts and chemical appliance parts.
Aromatic polyamide resins, however, generally have poor flame retardancy. A halogen flame retardant can be added to achieve a flame retardancy of UL-94 V-0. Increasingly, however, regulations, such as the Restriction of the Use of Certain Hazardous Substance (RoHS) and Prohibition of the Certain Hazardous Substance (PoHS), prohibit the use of halogenated flame retardants in various products, such as electrical/electronic instrument parts.
US Publication No. 2007-0054992 discloses a polyamide resin composition including a non-halogen flame retardant. However, the polyamide resin composition can exhibit deteriorated heat-resistance and other mechanical properties, due to the use of the flame retardant in high amounts to obtain V-0 flame retardancy. In addition, the processing temperature can be increased, there can be increased gas emissions due to decomposition of the flame retardant, and there can be problems relating to corrosion of an injection molding machine and a mold.
In order to reduce the amount of flame retardant in polyamide resin compositions, the use of polyphenylene sulfide resin has been proposed. Polyphenylene sulfide resin, as a thermoplastic resin, can have excellent properties such as heat-resistance, dimensional stability, chemical resistance, flame retardancy, and processibility. Reinforced polyphenylene sulfide resin can replace metal materials used in precision parts, such as various optical parts or electrical/electronic instrument parts.
Adding polyphenylene sulfide resin to the polyamide resin composition can reduce the amount of the flame retardant required. However, this does not prevent gas blister formation on a surface of a product due to out-gassing when the composition is processed at high temperatures. Also, if a phenol antioxidant is used, there can be increased gas blister formation on a surface due to moisture absorption.